Preheat the oven to 425F degrees. Line a 12 cavity muffin pan with muffin papers, or spray with non-stick cooking spray and flour. You'll end up with about 12-14 muffins total, so you may need 2 tins.
In a medium bowl whisk together the flour, cocoa, baking powder, baking soda and salt. Set aside.
Using a hand held or stand mixer or whisk, beat together the oil and sugars on until no lumps remain. Then add in the eggs and vanilla and continue mixing for about 30 seconds.
Turn off the mixer and scrape down the sides of the bowl.
Mix the mashed bananas and yogurt into the oil mixture.
Carefully fold in the dry ingredients using a rubber spatula or wooden spoon. Be very careful not to over mix - the batter will be thick.
Fold in the chocolate chips.
Spoon 1/3 cup of muffin batter into the cavities of your prepared muffin pan. You'll end up with 12-14 muffins total.
Bake at 425F for 5 minutes, then turn down your oven to 375F (you won't need to remove the muffins from your oven) and continue baking for 10-12 minutes until the tops are set and a toothpick comes out clean.
Let to cool in the pan for 10 minutes, then remove and continue cooling on a wire rack.